Piezoelectric mems microphone

ABSTRACT

A piezoelectric microelectromechanical systems microphone can be mounted on a printed circuit board. The microphone can include a substrate with an opening between a bottom end of the substrate and a top end of the substrate. The microphone can include a single piezoelectric film layer disposed over the top end of the substrate and defining a diaphragm structure, the single piezoelectric film layer having substantially zero residual stress and formed from a piezoelectric wafer. The microphone can include one or more electrodes disposed over the diaphragm structure. The diaphragm structure is configured to deflect when subjected to sound pressure via the opening in the substrate.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet as filed with the presentapplication are hereby incorporated by reference under 37 CFR 1.57.

BACKGROUND OF THE INVENTION Field

The present disclosure is directed to a piezoelectricmicroelectromechanical systems (MEMS) microphone, and in particular to asingle piezoelectric layer MEMS microphone.

Description of the Related Art

A MEMS microphone is a micro-machined electromechanical device used toconvert sound pressure (e.g., voice sound) to an electrical signal(e.g., voltage). MEMS microphones are widely used in mobile devices,headsets, smart speakers and other voice-interface devices or systems.Conventional capacitive MEMS microphones suffer from high powerconsumption (e.g., large bias voltage) and reliability, for example whenused in a harsh environment (e.g., when exposed to dust and/or water).

Piezoelectric MEMS microphones have been used to address thedeficiencies of capacitive MEMS microphones. Piezoelectric MEMSmicrophones offer a constant listening capability while consuming almostno power (e.g., no bias voltage is needed), are robust and immune towater and dust contamination. Existing piezoelectric MEMS microphonesare based on either a cantilever MEMS structure or a diaphragm MEMSstructure, and is mostly based on sputter-deposited thin filmpiezoelectric structure. Such thin piezoelectric film suffers from largeresidual stress after deposition which results in sensitivitydegradation and variation.

The cantilever MEMS structure suffers from poor low-frequency roll-offcontrol as the gap between cantilevers varies due to cantileverdeflection induced by residual stress. Additionally, the cantilever MEMSstructure with gap control mechanism can have a complex structure thatresults in higher manufacturing costs and poor reliability performance.The diaphragm MEMS structure provides better low-frequency roll-offcontrol and higher sensitivity than the cantilever MEMS structure, butsuffers from sensitivity variation as residual stress causes largetensile or compression stresses within the diaphragm (e.g., a smallresidual stress results in a large sensitivity degradation for diaphragmtype piezoelectric MEMS microphone).

SUMMARY

Accordingly, there is a need for an improved piezoelectric MEMSmicrophone that does not suffer the deficiencies in existing MEMScantilever and diaphragm structures.

In accordance with one aspect of the disclosure, a piezoelectric MEMSmicrophone has a single layer of stress-free piezoelectric film. Thesingle layer piezoelectric film is formed from a piezoelectric substrateor wafer via, for example, wafer-bonding techniques (e.g., direct oradhesive bonding techniques) and thinning techniques (e.g., ion slicing,Chemical Mechanical Polishing (CMP)). Advantageously, the stress-freesingle-layer piezoelectric MEMS microphone can provide one or more ofhigh and uniform sensitivity, precise low-frequency roll-off control,low part to part variation and high yield (e.g., zero stress variationacross the wafer).

In accordance with one aspect of the disclosure, a piezoelectricmicroelectromechanical systems microphone is provided. The microphonecomprises a substrate defining an opening between a bottom end of thesubstrate and a top end of the substrate. The microphone also comprisesa single piezoelectric film layer disposed over the top end of thesubstrate and defining a diaphragm structure. The single piezoelectricfilm layer being substantially flat with substantially zero residualstress. The microphone also comprises an electrode disposed over thediaphragm structure. The diaphragm structure is configured to deflectwhen subjected to sound pressure via the opening in the substrate.

In accordance with another aspect of the disclosure, a radiofrequencymodule is provided. The radiofrequency module comprises a printedcircuit board including a substrate layer. The radiofrequency modulealso comprises one or more piezoelectric microelectromechanical systemsmicrophones mounted on the printed circuit board. Each microphoneincludes a substrate defining an opening between a bottom end of thesubstrate and a top end of the substrate. A single piezoelectric filmlayer is disposed over the top end of the substrate and defines adiaphragm structure, the single piezoelectric film layer beingsubstantially flat with substantially zero residual stress. An electrodeis disposed over the diaphragm structure. The diaphragm structure isconfigured to deflect when subjected to sound pressure via the openingin the substrate.

In accordance with another aspect of the disclosure, a wireless mobiledevice is provided. The wireless mobile device comprises one or moreantennas, a front end system that communicates with the one or moreantennas, and one or more one or more piezoelectricmicroelectromechanical systems microphones mounted on a substrate layer.Each microphone includes a substrate defining an opening between abottom end of the substrate and a top end of the substrate. A singlepiezoelectric film layer is disposed over the top end of the substrateand defines a diaphragm structure, the single piezoelectric film layerbeing substantially flat with substantially zero residual stress. Anelectrode is disposed over the diaphragm structure. The diaphragmstructure is configured to deflect when subjected to sound pressure viathe opening in the substrate.

In accordance with another aspect of the disclosure, a method of makinga piezoelectric microelectromechanical systems microphone is provided.The method comprises the steps of: a) oxidizing a top surface and abottom surface of a substrate to form a top oxidation layer and a bottomoxidation layer, b) applying a piezoelectric wafer over the top surfaceof the substrate, the piezoelectric wafer defining a substantially flatstructure with substantially zero residual stress, c) thinning thepiezoelectric wafer to define a single piezoelectric film layer thatdefines a substantially flat diaphragm structure with substantially zeroresidual stress, d) forming or applying an electrode over the singlepiezoelectric film layer, and e) etching the bottom oxidation layer andsubstrate to form an opening in the substrate. The opening allows soundpressure to travel through the opening to deflect the diaphragmstructure.

In accordance with another aspect of the disclosure, a method of makinga radiofrequency module is provided. The method comprises the steps offorming or providing a printed circuit board that includes a substratelayer, and forming or providing one or more piezoelectricmicroelectromechanical systems microphones. The process of forming orproviding one or more piezoelectric microelectromechanical systemsmicrophones comprises: (a) oxidizing a top surface and a bottom surfaceof a substrate to form a top oxidation layer and a bottom oxidationlayer, (b) applying a piezoelectric wafer over the top surface of thesubstrate, the piezoelectric wafer defining a substantially flatstructure with substantially zero residual stress, (c) thinning thepiezoelectric wafer to define a single piezoelectric film layer thatdefines a substantially flat diaphragm structure with substantially zeroresidual stress, (d) forming or applying an electrode over the singlepiezoelectric film layer, and (e) etching the bottom oxidation layer andsubstrate to form an opening in the substrate. The opening allows soundpressure to travel through the opening to deflect the diaphragmstructure. The method of making the radiofrequency module also comprisesthe step of mounting the one or more piezoelectricmicroelectromechanical systems microphones on the printed circuit board.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of one embodiment of a wireless device.

FIG. 2A is a schematic diagram of one embodiment of a packaged module.

FIG. 2B is a schematic diagram of a cross-section of the packaged moduleof FIG. 2A taken along the lines 2B-2B.

FIG. 3 is a top view of a piezoelectric MEMS circular microphone.

FIG. 4 is a cross-sectional side view of the piezoelectric MEMSmicrophone of FIG. 3 .

FIG. 5 is a top view of a piezoelectric MEMS rectangular microphone.

FIG. 6 is a cross-sectional side view of the piezoelectric MEMSmicrophone of FIG. 5 .

FIG. 7 is a top view of a piezoelectric MEMS circular microphone.

FIG. 8 is a cross-sectional side view of the piezoelectric MEMSmicrophone of FIG. 8 .

FIG. 9A is a cross-sectional side view of one step in the manufacture ofa piezoelectric MEMS microphone.

FIG. 9B is a cross-sectional side view of another step in themanufacture of a piezoelectric MEMS microphone.

FIG. 9C is a cross-sectional side view of another step in themanufacture of a piezoelectric MEMS microphone.

FIG. 9D is a cross-sectional side view of another step in themanufacture of a piezoelectric MEMS microphone.

FIG. 9E is a cross-sectional side view of another step in themanufacture of a piezoelectric MEMS microphone.

FIG. 9F is a cross-sectional side view of another step in themanufacture of a piezoelectric MEMS microphone.

FIG. 9G is a cross-sectional side view of another step in themanufacture of a piezoelectric MEMS microphone.

FIG. 9H is a cross-sectional side view of another step in themanufacture of a piezoelectric MEMS microphone.

FIG. 9I is a cross-sectional side view of another step in themanufacture of a piezoelectric MEMS microphone.

FIG. 9J is a cross-sectional side view of another step in themanufacture of a piezoelectric MEMS microphone.

FIG. 10A is a cross-sectional side view of one step in the manufactureof a piezoelectric MEMS microphone.

FIG. 10B is a cross-sectional side view of another step in themanufacture of a piezoelectric MEMS microphone.

FIG. 10C is a cross-sectional side view of another step in themanufacture of a piezoelectric MEMS microphone.

FIG. 10D is a cross-sectional side view of another step in themanufacture of a piezoelectric MEMS microphone.

FIG. 10E is a cross-sectional side view of another step in themanufacture of a piezoelectric MEMS microphone.

FIG. 10F is a cross-sectional side view of another step in themanufacture of a piezoelectric MEMS microphone.

FIG. 10G is a cross-sectional side view of another step in themanufacture of a piezoelectric MEMS microphone.

FIG. 10H is a cross-sectional side view of another step in themanufacture of a piezoelectric MEMS microphone.

FIG. 10I is a cross-sectional side view of another step in themanufacture of a piezoelectric MEMS microphone.

FIG. 10J is a cross-sectional side view of another step in themanufacture of a piezoelectric MEMS microphone.

FIG. 11A is a cross-sectional side view of one step in the manufactureof a piezoelectric MEMS microphone.

FIG. 11B is a cross-sectional side view of another step in themanufacture of a piezoelectric MEMS microphone.

FIG. 11C is a cross-sectional side view of another step in themanufacture of a piezoelectric MEMS microphone.

FIG. 11D is a cross-sectional side view of another step in themanufacture of a piezoelectric MEMS microphone.

FIG. 11E is a cross-sectional side view of another step in themanufacture of a piezoelectric MEMS microphone.

FIG. 11F is a cross-sectional side view of another step in themanufacture of a piezoelectric MEMS microphone.

FIG. 11G is a cross-sectional side view of another step in themanufacture of a piezoelectric MEMS microphone.

FIG. 11H is a cross-sectional side view of another step in themanufacture of a piezoelectric MEMS microphone.

FIG. 11I is a cross-sectional side view of another step in themanufacture of a piezoelectric MEMS microphone.

DETAILED DESCRIPTION

The following detailed description of certain embodiments presentsvarious descriptions of specific embodiments. However, the innovationsdescribed herein can be embodied in a multitude of different ways, forexample, as defined and covered by the claims. In this description,reference is made to the drawings were like reference numerals canindicate identical or functionally similar elements. It will beunderstood that elements illustrated in the figures are not necessarilydrawn to scale. Moreover, it will be understood that certain embodimentscan include more elements than illustrated in a drawing and/or a subsetof the elements illustrated in a drawing. Further, some embodiments canincorporate any suitable combination of features from two or moredrawings.

The International Telecommunication Union (ITU) is a specialized agencyof the United Nations (UN) responsible for global issues concerninginformation and communication technologies, including the shared globaluse of radio spectrum.

The 3rd Generation Partnership Project (3GPP) is a collaboration betweengroups of telecommunications standard bodies across the world, such asthe Association of Radio Industries and Businesses (ARIB), theTelecommunications Technology Committee (TTC), the China CommunicationsStandards Association (CCSA), the Alliance for TelecommunicationsIndustry Solutions (ATIS), the Telecommunications Technology Association(TTA), the European Telecommunications Standards Institute (ETSI), andthe Telecommunications Standards Development Society, India (TSDSI).

Working within the scope of the ITU, 3GPP develops and maintainstechnical specifications for a variety of mobile communicationtechnologies, including, for example, second generation (2G) technology(for instance, Global System for Mobile Communications (GSM) andEnhanced Data Rates for GSM Evolution (EDGE)), third generation (3G)technology (for instance, Universal Mobile Telecommunications System(UMTS) and High Speed Packet Access (HSPA)), and fourth generation (4G)technology (for instance, Long Term Evolution (LTE) and LTE-Advanced).

The technical specifications controlled by 3GPP can be expanded andrevised by specification releases, which can span multiple years andspecify a breadth of new features and evolutions.

In one example, 3GPP introduced carrier aggregation (CA) for LTE inRelease 10. Although initially introduced with two downlink carriers,3GPP expanded carrier aggregation in Release 14 to include up to fivedownlink carriers and up to three uplink carriers. Other examples of newfeatures and evolutions provided by 3GPP releases include, but are notlimited to, License Assisted Access (LAA), enhanced LAA (eLAA),Narrowband Internet-of-Things (NB-IOT), Vehicle-to-Everything (V2X), andHigh Power User Equipment (HPUE).

3GPP introduced Phase 1 of fifth generation (5G) technology in Release15 and plans to introduce Phase 2 of 5G technology in Release 16(targeted for 2019). Subsequent 3GPP releases will further evolve andexpand 5G technology. 5G technology is also referred to herein as 5G NewRadio (NR).

5G NR supports or plans to support a variety of features, such ascommunications over millimeter wave spectrum, beam forming capability,high spectral efficiency waveforms, low latency communications, multipleradio numerology, and/or non-orthogonal multiple access (NOMA). Althoughsuch RF functionalities offer flexibility to networks and enhance userdata rates, supporting such features can pose a number of technicalchallenges.

The teachings herein are applicable to a wide variety of communicationsystems, including, but not limited to, communication systems usingadvanced cellular technologies, such as LTE-Advanced, LTE-Advanced Pro,and/or 5G NR.

FIG. 1 is a schematic diagram of one embodiment of a wireless device100. The wireless device 100 can be, for example but not limited to, aportable telecommunication device such as a mobile cellular-typetelephone. The wireless device 100 can include one or more of a basebandsystem 101, a transceiver 102, a front end system 103, one or moreantennas 104, a power management system 105, a memory 106, a userinterface 107, a battery 108 (e.g., direct current (DC) battery), and amicrophone 300 (e.g., a piezoelectric MEMS microphone). Other additionalcomponents, such as a speaker, display and keyboard can optionally beconnected to the baseband system 101. The battery 108 can provide powerto the wireless device 100. The microphone 300 can supply signals to thebaseband system 101.

It should be noted that, for simplicity, only certain components of thewireless device 100 are illustrated herein. The control signals providedby the baseband system 101 control the various components within thewireless device 100. Further, the function of the transceiver 102 can beintegrated into separate transmitter and receiver components.

The wireless device 100 can be used communicate using a wide variety ofcommunications technologies, including, but not limited to, 2G, 3G, 4G(including LTE, LTE-Advanced, and LTE-Advanced Pro), 5G NR, WLAN (forinstance, Wi-Fi), WPAN (for instance, Bluetooth and ZigBee), WMAN (forinstance, WiMax), and/or GPS technologies.

The transceiver 102 generates RF signals for transmission and processesincoming RF signals received from the antennas 104. It will beunderstood that various functionalities associated with the transmissionand receiving of RF signals can be achieved by one or more componentsthat are collectively represented in FIG. 1 as the transceiver 102. Inone example, separate components (for instance, separate circuits ordies) can be provided for handling certain types of RF signals.

The front end system 103 aids in conditioning signals transmitted toand/or received from the antennas 104. In the illustrated embodiment,the front end system 103 includes one or more power amplifiers (PAs)111, low noise amplifiers (LNAs) 112, filters 113, switches 114, andduplexers 115. However, other implementations are possible.

For example, the front end system 103 can provide a number offunctionalities, including, but not limited to, amplifying signals fortransmission, amplifying received signals, filtering signals, switchingbetween different bands, switching between different power modes,switching between transmission and receiving modes, duplexing ofsignals, multiplexing of signals (for instance, diplexing ortriplexing), or some combination thereof.

In certain implementations, the wireless device 100 supports carrieraggregation, thereby providing flexibility to increase peak data rates.Carrier aggregation can be used for both Frequency Division Duplexing(FDD) and Time Division Duplexing (TDD), and may be used to aggregate aplurality of carriers or channels. Carrier aggregation includescontiguous aggregation, in which contiguous carriers within the sameoperating frequency band are aggregated. Carrier aggregation can also benon-contiguous, and can include carriers separated in frequency within acommon band or in different bands.

The antennas 104 can include antennas used for a wide variety of typesof communications. For example, the antennas 104 can include antennasfor transmitting and/or receiving signals associated with a wide varietyof frequencies and communications standards.

In certain implementations, the antennas 104 support MIMO communicationsand/or switched diversity communications. For example, MIMOcommunications use multiple antennas for communicating multiple datastreams over a single radio frequency channel. MIMO communicationsbenefit from higher signal to noise ratio, improved coding, and/orreduced signal interference due to spatial multiplexing differences ofthe radio environment. Switched diversity refers to communications inwhich a particular antenna is selected for operation at a particulartime. For example, a switch can be used to select a particular antennafrom a group of antennas based on a variety of factors, such as anobserved bit error rate and/or a signal strength indicator.

The wireless device 100 can operate with beamforming in certainimplementations. For example, the front end system 103 can include phaseshifters having variable phase controlled by the transceiver 102.Additionally, the phase shifters are controlled to provide beamformation and directivity for transmission and/or reception of signalsusing the antennas 104. For example, in the context of signaltransmission, the phases of the transmit signals provided to theantennas 104 are controlled such that radiated signals from the antennas104 combine using constructive and destructive interference to generatean aggregate transmit signal exhibiting beam-like qualities with moresignal strength propagating in a given direction. In the context ofsignal reception, the phases are controlled such that more signal energyis received when the signal is arriving to the antennas 104 from aparticular direction. In certain implementations, the antennas 104include one or more arrays of antenna elements to enhance beamforming.

The baseband system 101 is coupled to the user interface 107 tofacilitate processing of various user input and output (I/O), such asvoice and data. The baseband system 101 provides the transceiver 102with digital representations of transmit signals, which the transceiver102 processes to generate RF signals for transmission. The basebandsystem 101 also processes digital representations of received signalsprovided by the transceiver 102. As shown in FIG. 1 , the basebandsystem 101 is coupled to the memory 106 of facilitate operation of thewireless device 100.

The memory 106 can be used for a wide variety of purposes, such asstoring data and/or instructions to facilitate the operation of thewireless device 100 and/or to provide storage of user information.

The power management system 105 provides a number of power managementfunctions of the wireless device 100. In certain implementations, thepower management system 105 includes a PA supply control circuit thatcontrols the supply voltages of the power amplifiers 111. For example,the power management system 105 can be configured to change the supplyvoltage(s) provided to one or more of the power amplifiers 111 toimprove efficiency, such as power added efficiency (PAE).

As shown in FIG. 1 , the power management system 105 receives a batteryvoltage from the battery 108. The battery 108 can be any suitablebattery for use in the wireless device 100, including, for example, alithium-ion battery.

FIG. 2A is a schematic diagram of one embodiment of a packaged module200. FIG. 2B is a schematic diagram of a cross-section of the packagedmodule 200 of FIG. 2A taken along the lines 2B-2B.

The packaged module 200 includes radio frequency components 201, asemiconductor die 202, surface mount devices 203, wirebonds 208, apackage substrate 230, and an encapsulation structure 240. One or moreof the surface mounted devices (SMDs) 203 can be a microphone 300 (e.g.,a piezoelectric MEMS microphone). The package substrate 230 includespads 206 formed from conductors disposed therein. Additionally, thesemiconductor die 202 includes pins or pads 204, and the wirebonds 208have been used to connect the pads 204 of the die 202 to the pads 206 ofthe package substrate 220.

The semiconductor die 202 includes a power amplifier 245, which can beimplemented in accordance with one or more features disclosed herein.

The packaging substrate 230 can be configured to receive a plurality ofcomponents such as radio frequency components 201, the semiconductor die202 and the surface mount devices 203, which can include, for example,surface mount capacitors and/or inductors. In one implementation, theradio frequency components 201 include integrated passive devices(IPDs).

As shown in FIG. 2B, the packaged module 200 is shown to include aplurality of contact pads 232 disposed on the side of the packagedmodule 200 opposite the side used to mount the semiconductor die 202.Configuring the packaged module 200 in this manner can aid in connectingthe packaged module 200 to a circuit board, such as a phone board of amobile device. The example contact pads 232 can be configured to provideradio frequency signals, bias signals, and/or power (for example, apower supply voltage and ground) to the semiconductor die 202 and/orother components. As shown in FIG. 2B, the electrical connectionsbetween the contact pads 232 and the semiconductor die 202 can befacilitated by connections 233 through the package substrate 230. Theconnections 233 can represent electrical paths formed through thepackage substrate 220, such as connections associated with vias andconductors of a multilayer laminated package substrate.

In some embodiments, the packaged module 200 can also include one ormore packaging structures to, for example, provide protection and/orfacilitate handling. Such a packaging structure can include overmold orencapsulation structure 240 formed over the packaging substrate 230 andthe components and die(s) disposed thereon.

It will be understood that although the packaged module 200 is describedin the context of electrical connections based on wirebonds, one or morefeatures of the present disclosure can also be implemented in otherpackaging configurations, including, for example, flip-chipconfigurations.

Piezoelectric MEMS Microphone

FIGS. 3-4 show one implementation of a piezoelectricmicroelectromechanical systems (MEMS) microphone 300A (hereinafter the“microphone”). The microphone 300A is optionally a piezoelectric MEMSdiaphragm microphone 300A. The microphone 300A has a substrate 301. Thesubstrate 301 is optionally made of Silicon. An insulation layer 311 isdisposed on a surface of the substrate 301. The insulation layer 311 isoptionally silicon dioxide.

A piezoelectric film layer 309 (e.g., a single piezoelectric film layer309) is disposed (e.g., adhered) on the oxide layer 311. Thepiezoelectric film layer 309 is substantially stress-free (e.g., haszero residual stress) and is optionally formed from a piezoelectricsubstrate 310. Optionally, the piezoelectric substrate 310 is planar(e.g., flat). In one implementation, the piezoelectric substrate 310 ismade of Lithium Niobate (LiNbO3). In another implementation, thepiezoelectric substrate 310 is made of Lithium Tantalate (LiTaO3). Thepiezoelectric substrate 310 is used to form the piezoelectric film 309(e.g., that is substantially stress-free, that has zero residual stress)via wafer-bonding techniques (e.g., direct or adhesive bonding) andthinning techniques (e.g., ion slicing and Chemical Mechanical Polishing(CMP)), as further discussed below. Advantageously, the stress-freesingle layer piezoelectric MEMS microphone 300A can provide one or moreof a high and uniform sensitivity, precise low-frequency roll-offcontrol, low part to part variation and high yield (e.g., zero stressvariation across the wafer).

An electrode 315 (e.g., a “top” electrode) is disposed on top of thepiezoelectric film layer 309, and a passivation layer 318 is disposedover the electrode 315 and at least partially defines a top surface ofthe microphone 300A. Optionally, the electrode 315 is made of Molybdenum(Mo). In one implementation, the passivation layer 318 is optionallytitanium nitride (TiN). The piezoelectric film layer (e.g., the singlepiezoelectric film layer) 309 defines a diaphragm 319.

With reference to FIG. 3 , the microphone 300A can have a generallycircular or round shape. However, as discussed further below, themicrophone 300A can have other suitable shapes. The electrode 315 caninclude an outer circumferential electrode 302 and a center electrode305. The outer circumferential electrode 302 can optionally be dividedinto two or more portions 302A-302F (e.g., six portions) by one or moregaps 303 between the portions 302A-302F. Optionally, the gaps 303 cancompletely separate the portions 302A-302F. The center electrode 305 canoptionally be divided into two or more portions 305A-305F (e.g., sixportions) by one or more gaps 307 between the portions 305A-305F.

The number of portions that the center electrode 305 and outercircumferential electrode 302 are divided into can be determined via asimulation starting with a single center electrode and a single outercircumferential electrode to evaluate output voltage distributionrelative to degrees around the circumference of the electrodes 302, 305.The number of portions that the center electrode 305 and outercircumferential electrode 302 are divided into can also depend on a cutangle of the piezoelectric substrate or wafer 310. Though FIGS. 3-4 showthe center electrode 305 and outer circumferential electrode 302 dividedinto six portions each 305A-305F, 302A-302F, the number of portions canvary (e.g., based on the cut angle of the piezoelectric wafer 310).

Optionally, the gaps 307 can completely separate the portions 305A-305F.The gaps 303 can advantageously control the amount of capacitanceprovided by the electrodes 302 (e.g., if want a higher capacitance thenfewer gaps 303 are provided; if want a lower capacitance then more gaps303 are provided). The reduction in capacitance (e.g., due to increasednumber of gaps 303) results in increased sensitivity, and the increasein capacitance (e.g., due to reduced number of gaps 303) results inreduced sensitivity. Therefore, sensitivity and capacitance canadvantageously be balanced as desired via the use of such gaps 303, 307to divide the electrodes 302, 305.

With reference to FIG. 3 , each of the portions 305A-305F of the centerelectrode 305 is connected in series with one of the portions 302A-302Fof the circumferential electrode 302 via a connection via 304. Themicrophone 300A can have one or more bond pads 316 connected to thecircumferential electrode 302 and center electrode 305. Each of thecenter electrode portions 305A-305F defines a capacitor with an opposingouter circumferential electrode portion 302A-302F with the piezoelectricfilm 309 in between, where the center electrode portions 305A-305F havea different polarity than the outer circumferential electrode portions302A-302F, the electric field extends horizontally (along same plane)and lateral capacitance exists between the center electrode portions305A-305F and the outer circumferential electrode portions 302A-302F.

With respect to FIG. 3 , the electrical signal travels laterally (e.g.,along same plane) from one bond pad 316 to center electrode portion305F, then to outer circumferential electrode portion 302F via thepiezoelectric film 309, then to center electrode portion 305A viaconnector 304, then to outer circumferential electrode portion 302A viathe piezoelectric film 309, then to center electrode portion 305B viaconnector 304, then to outer circumferential electrode portion 302B viathe piezoelectric film 309, then to center electrode portion 305C viaconnector 304, then to outer circumferential electrode portion 302C viathe piezoelectric film 309, then to center electrode portion 305D viaconnector 304, then to outer circumferential electrode portion 302D viathe piezoelectric film 309, then to center electrode portion 305E viaconnector 304, then to outer circumferential electrode portion 302E viathe piezoelectric film 309, then to bond pad 316.

The center electrode 305 can be spaced from the circumferentialelectrode 302 so that the center electrode 305 is substantially centeredrelative to the circumferential electrode 302 (e.g., both electrodes302, 305 have the same central axis), with at least a portion of thediaphragm 319 extending between the circumferential electrode 302 andthe center electrode 305. As shown in FIGS. 3-4 , the diaphragm 319 canextend beneath the circumferential electrode 302 and beneath the centerelectrode 305 of the electrode 315. A through hole 317 can be formed(e.g., etched) in the diaphragm 319 (e.g., in the piezoelectric filmlayer 309 that defines the diaphragm 319) at a location between thecircumferential electrode 302 and the center electrode 305. The throughhole 317 can extend from a top surface of the diaphragm 319 to a bottomsurface of the diaphragm 319 to thereby extend completely through thediaphragm 319. The microphone 300A can have an opening 320 in thesubstrate 301 that is located underneath the diaphragm 319, which allowsthe diaphragm 319 to move (e.g., deflect).

With continued reference to FIG. 3 , the electrodes 302, 305 areadvantageously located (e.g., electrode 302 along the periphery andelectrode 305 at the center of the diaphragm structure 319) where thehighest stress, therefore highest output voltage or electrical energyvia piezoelectric effect, is induced by sound pressure exerted on thediaphragm 319 (e.g., via air pressure delivered through the opening 320toward the diaphragm 319). As discussed further below, the piezoelectricfilm layer 309 can be a single layer that is substantially stress-free(e.g., that has zero residual stress).

Advantageously, the piezoelectric MEMS microphone 300A has a simplifiedmanufacturing process (i.e., is simpler to manufacture), for examplebecause only a top layer of electrodes is used (i.e., do not use aseparate, such as middle or lower, layer of electrodes). However, thepiezoelectric MEMS microphone 300A exhibits a smaller capacitance thanmicrophones with multiple layers of electrodes (such as piezoelectricMEMS microphone 300C, described further below). For example, thepiezoelectric MEMS microphone 300A can exhibit a capacitance level thatis 1-2 orders of magnitude lower than similar microphones with multiplelayers of electrodes.

FIGS. 5-6 show another implementation of a piezoelectricmicroelectromechanical systems (MEMS) microphone 300B (hereinafter the“microphone”). The microphone 300B is optionally a piezoelectric MEMSdiaphragm microphone 300B. The substrate 301′ is optionally made ofSilicon. An insulation layer 311′ is disposed on a surface of thesubstrate 301′. The insulation layer 311′ is optionally Silicon dioxide.A piezoelectric film layer 309′ (e.g., a single piezoelectric filmlayer) is disposed on the insulation layer 311′. The piezoelectric filmlayer 309′ is optionally made from a piezoelectric substrate 310′. Inone implementation, the piezoelectric substrate 310′ is made of LithiumNiobate (LiNbO3). In another implementation, the piezoelectric substrate310′ is made of Lithium Tantalate (LiTaO3). An electrode 315′ (e.g., a“top” electrode) is disposed on top of the piezoelectric film layer309′, and a passivation layer 318′ is disposed over the electrode 315′and at least partially defines a top surface of the microphone 300B. Inone implementation, the passivation layer 318′ is optionally titaniumnitride (TiN). The piezoelectric film layer 309′ (e.g. the singlepiezoelectric film layer) defines a diaphragm 319′.

With reference to FIG. 5 , the microphone 300B can have a generallyrectangular (e.g., square) shape. However, the microphone 300B can haveother suitable shapes. The electrode 315′ can include one or more sideelectrodes 302′ adjacent one or more sides of the diaphragm 319′ and oneor more center electrodes 305′. In FIG. 5 , the electrode 315′ includesfour side electrodes 302A′-302D′, each adjacent a side of therectangular (e.g., square) shape of the diaphragm 319′. Each of the sideelectrodes 302′ can optionally be a single piece (e.g., not divided intodifferent portions by one or more gaps between the portions). The gapscan advantageously control the amount of capacitance provided by theelectrodes 302′ (e.g., if want a higher capacitance then fewer gaps areprovided; if want a lower capacitance then more gaps are provided). Thereduction in capacitance (e.g., due to increased number of gaps) resultsin increased sensitivity, and the increase in capacitance (e.g., due toreduced number of gaps) results in reduced sensitivity. Therefore,sensitivity and capacitance can advantageously be balanced as desiredvia the use of such gaps to divide the electrodes 302′.

The center electrode 305′ can optionally be divided into two or moreportions 305A′-305D′ (e.g., four portions) by one or more gaps 307′between the portions 305A′-305D′. Optionally, the gaps 307′ cancompletely separate the portions 305A′-305D′. The gaps 307′ canadvantageously control the amount of capacitance provided by theelectrodes 3′05 (e.g., if want a higher capacitance then fewer gaps 307′are provided; if want a lower capacitance then more gaps 307′ areprovided). The reduction in capacitance (e.g., due to increased numberof gaps 307′) results in increased sensitivity, and the increase incapacitance (e.g., due to reduced number of gaps 307′) results inreduced sensitivity. Therefore, sensitivity and capacitance canadvantageously be balanced as desired via the use of such gaps 307′ todivide the electrode 305′.

With reference to FIG. 5 , each of the portions 305A′-305D′ of thecenter electrode 305′ is connected in series with one of the sideelectrodes 302A′-302D′ via a connection via 304′. The microphone 300Bcan have one or more bond pads 316′ connected to the peripheralelectrode 302′ and center electrode 305′.

The number of portions that the center electrode 305′ and side electrode302′ are divided into can be determined via a simulation starting with asingle center electrode and a single outer peripheral electrode toevaluate output voltage distribution relative to degrees around thecircumference of the electrodes 302′, 305′. The number of portions thatthe center electrode 305′ and outer peripheral electrode 302′ aredivided into can also depend on a cut angle of the piezoelectricsubstrate or wafer 310′. Though FIGS. 5-6 show the center electrode 305′and outer peripheral electrode 302′ divided into four portions each305A′-305D′, 302A-302F, the number of portions can vary (e.g., based onthe cut angle of the piezoelectric wafer 310′).

Optionally, the gaps 307′ can completely separate the portions305A′-305D′. The gaps 303′ can advantageously control the amount ofcapacitance provided by the electrodes 302′ (e.g., if want a highercapacitance then fewer gaps 303′ are provided; if want a lowercapacitance then more gaps 303′ are provided). The reduction incapacitance (e.g., due to increased number of gaps 303′) results inincreased sensitivity, and the increase in capacitance (e.g., due toreduced number of gaps 303′) results in reduced sensitivity. Therefore,sensitivity and capacitance can advantageously be balanced as desiredvia the use of such gaps 303′, 307′ to divide the electrodes 302′, 305′.

With reference to FIG. 5 , each of the portions 305A′-305D′ of thecenter electrode 305′ is connected in series with one of the portions302A′-302D′ of the peripheral electrode 302′ via a connection via 304′.The microphone 300B can have one or more bond pads 316′ connected to theperipheral electrode 302′ and center electrode 305′. Each of the centerelectrode portions 305A-305D′ defines a capacitor with an opposing sideelectrode portion 302A′-302D′ with the piezoelectric film 309′ inbetween, where the center electrode portions 305A′-305D′ have adifferent polarity than the side electrode portions 302A′-302D′, theelectric field extends horizontally (along same plane) and lateralcapacitance exists between the center electrode portions 305A′-305D′ andthe side electrode portions 302A′-302D′.

With respect to FIG. 5 , the electrical signal travels laterally (e.g.,along same plane) from one bond pad 316′ to center electrode portion305A′, then to side electrode portion 302A′ via the piezoelectric film309′, then to center electrode portion 305B′ via connector 304′, then toside electrode portion 302B′ via the piezoelectric film 309′, then tocenter electrode portion 305C′ via connector 304′, then to sideelectrode portion 302C′ via the piezoelectric film 309′, then to centerelectrode portion 305D′ via connector 304′, then to side electrodeportion 302D′, then to bond pad 316′.

The center electrode 305′ can be spaced from the peripheral electrode302′ so that the center electrode 305′ is substantially centeredrelative to the peripheral electrode 302′ (e.g., both electrodes 302′,305′ have the same central axis), with at least a portion of thediaphragm 319′ extending between the peripheral electrode 302′ and thecenter electrode 305′. As shown in FIGS. 5-6 , the diaphragm 319′ canextend beneath the peripheral electrode 302′ and beneath the centerelectrode 305′ of the electrode 315′. A through hole 317′ can be formed(e.g., etched) in the diaphragm 319′ (e.g., in the piezoelectric filmlayer 309′ that defines the diaphragm 319′) at a location between theperipheral electrode 302′ and the center electrode 305′. The throughhole 317′ can extend from a top surface of the diaphragm 319′ to abottom surface of the diaphragm 319′ to thereby extend completelythrough the diaphragm 319′. The microphone 300B can have an opening 320′in the substrate 301′ that is located underneath the diaphragm 319′,which allows the diaphragm 319′ to move (e.g., deflect).

With continued reference to FIG. 5 , the electrodes 302′, 305′ areadvantageously located (e.g., electrode 302′ along the periphery andelectrode 305′ at the center of the diaphragm structure 319′) where thehighest stress, therefore highest output voltage or electrical energyvia piezoelectric effect, is induced by sound pressure exerted on thediaphragm 319′ (e.g., via air pressure delivered through the opening320′ toward the diaphragm 319′). As discussed further below, thepiezoelectric film layer 309′ can be a single layer that issubstantially stress-free (e.g., that has zero residual stress).

As shown in FIGS. 5-6 , the diaphragm 319′ can extend beneath theperipheral electrode 302′ and beneath the center electrode 305′. Athrough hole 317′ can be formed (e.g., etched) in the diaphragm 319′(e.g., in the piezoelectric film layer 309′ that defines the diaphragm319′) at a location between the peripheral electrode 302′ and the centerelectrode 305′. The through hole 317′ can extend from a top surface ofthe diaphragm 319′ to a bottom surface of the diaphragm 319′ to therebyextend completely through the diaphragm 319′. The microphone 300B canhave an opening 320′ in the substrate 301′ that is located underneaththe diaphragm 319′, which allows the diaphragm 319′ to move.

With continued reference to FIG. 5 , the electrodes 302′, 305′ areadvantageously located where the highest stress is induced, thereforehighest output voltage or electrical energy via piezoelectric effect,(e.g., along the sides and center of the diaphragm structure 319′) bysound pressure exerted on the diaphragm 319′ (e.g., via air pressuredelivered through the opening 320′ toward the diaphragm 319′). Asdiscussed further below, the one or more piezoelectric film layers 309′can be a single layer that is substantially stress free (e.g., has zeroresidual stress), thereby advantageously providing a diaphragm structure319′ with approximately zero (e.g., zero) residual stress.

FIGS. 7-8 show one implementation of a piezoelectricmicroelectromechanical systems (MEMS) microphone 300C (hereinafter the“microphone”). The microphone 300C is optionally a piezoelectric MEMSdiaphragm microphone 300C. The microphone 300C has a substrate 301″. Thesubstrate 301″ is optionally made of Silicon. An insulation layer 311″is disposed on a surface of the substrate 301″. The insulation layer311″ is optionally silicon dioxide. An elastic layer 312″ is disposed onthe insulation layer 311″. The elastic layer 312″ can optionally be madeof Silicon Nitride. In another implementation, the elastic layer 312″can be made of a suitable or compatible dielectric material. The elasticlayer 312″ advantageously shifts a neutral axis of the piezoelectricMEMS microphone 300C, allowing a signal to be output between the middleelectrode 314″ and top electrode 315″ since they would have opposingpolarities.

A first electrode 314″ (e.g., a “middle” electrode) is disposed over theelastic layer 312″. A piezoelectric film layer 309″ (e.g., a singlepiezoelectric film layer 309″) is disposed on the first electrode 314″.The piezoelectric film layer 309″ is optionally made from apiezoelectric substrate 310″. In one implementation, the piezoelectricsubstrate 310″ is made of Lithium Niobate (LiNbO3). In anotherimplementation, the piezoelectric substrate 310′ is made of LithiumTantalate (LiTaO3). A second electrode 315″ (e.g., a “top” electrode) isdisposed on top of the piezoelectric film layer 309″, and a passivationlayer 318″ is disposed over the second electrode 315″ and at leastpartially defines a top surface of the microphone 300C. In oneimplementation, the passivation layer 318″ is optionally titaniumnitride (TiN). The piezoelectric film layer 309″ and elastic layer 312″define a diaphragm 319″. One or both of the first and second electrodes314″, 315″ can optionally be made of Molybdenum.

With reference to FIG. 7 , the microphone 300C can have a generallycircular or round shape. However, as discussed further herein, themicrophone 300C can have other suitable shapes. The second electrode315″ can include an outer circumferential electrode 302″ and a centerelectrode 305″. The outer circumferential electrode 302″ can optionallybe divided into two or more portions (e.g., six portions) 302A″-302F″ byone or more gaps 303″ between the portions 302A″-302F″. Optionally, thegaps 303″ can completely separate the portions 302A″-302F″. The centerelectrode 305″ can optionally be divided into two or more portions(e.g., six portions) 305A″-305F″ by one or more gaps 307″ between theportions 305A″-305F″.

The gaps 303″ can advantageously control the amount of capacitanceprovided by the electrodes 302″ (e.g., if want a higher capacitance thenfewer gaps 303″ are provided; if want a lower capacitance then more gaps303″ are provided). The reduction in capacitance (e.g., due to increasednumber of gaps 303″) results in increased sensitivity, and the increasein capacitance (e.g., due to reduced number of gaps 303″) results inreduced sensitivity. Therefore, sensitivity and capacitance canadvantageously be balanced as desired via the use of such gaps 303″,307″ to divide the electrodes 302″, 305″.

With reference to FIG. 7 , each of the portions 305A″-305F″ of thecenter electrode 305″ is connected in series with one of the portions302A″-302F″ of the circumferential electrode 302″ via a connection via304″. The microphone 300C can have one or more bond pads 316″ connectedto the circumferential electrode 302″ and center electrode 305″. Each ofthe center electrode portions 305A″-305F″ defines a capacitor with acorresponding portion underneath it of the middle electrode layer 314″,and each of the outer circumferential electrode portions 302A″-302F″defines a capacitor with a corresponding portion underneath it of themiddle electrode layer 314″, where the center electrode portions305A″-305F″ have a different polarity than the corresponding portionsbelow it from the middle electrode layer 314″, the electric fieldextends vertically (between the electrode layers 314″, 315″) andvertical capacitance exists therebetween. With respect to FIGS. 7-8 ,the electrical signal travels vertically between the top electrode 315″and middle electrode 314″.

The center electrode 305″ can be spaced from the circumferentialelectrode 302″ so that the center electrode 305″ is substantiallycentered relative to the circumferential electrode 302″ (e.g., bothelectrodes 302″, 305″ have the same central axis), with at least aportion of the diaphragm 319″ extending between the circumferentialelectrode 302″ and the center electrode 305″. As shown in FIGS. 7-8 ,the diaphragm 319″ can extend beneath the circumferential electrode 302″and beneath the center electrode 305″. A through hole 317″ can be formed(e.g., etched) in the diaphragm 319″ (e.g., in the piezoelectric filmlayer 309″ and elastic layer 312″ that define the diaphragm 319″) at alocation between the circumferential electrode 302″ and the centerelectrode 305″. The through hole 317″ can extend from a top surface ofthe diaphragm 319″ to a bottom surface of the diaphragm 319″ to therebyextend completely through the diaphragm 319″. The microphone 300C canhave an opening 320″ in the substrate 301″ that is located underneaththe diaphragm 319″, which allows the diaphragm 319″ to move (e.g.,deflect).

With continued reference to FIG. 7 , the electrodes 302″, 305″ areadvantageously located (e.g., electrode 302″ along the periphery andelectrode 305″ at the center of the diaphragm structure 319″) where thehighest stress, therefore highest output voltage or electrical energyvia piezoelectric effect, is induced by sound pressure exerted on thediaphragm 319″ (e.g., via air pressure delivered through the opening320″ toward the diaphragm 319″). As discussed further below, the singlepiezoelectric film layer 309″ can be advantageously be substantiallystress free, such as with approximately zero (e.g., zero) residualstress. Additionally, the microphone 300C advantageously has a largerrelative capacitance (e.g., with respect to microphones 300A, 300B).However, the microphone 300C can have output voltage that is smallerbecause of the increased number of layers in the microphone structure.

The through holes 317, 317′, 317″ in the diaphragms 319, 319′, 319″ ofthe microphones 300A, 300B, 300C can advantageously allow the lowfrequency roll off of the microphone 300A, 300B, 300C to be definedsubstantially precisely (e.g., at approximately 85 Hz±15 Hz, such as forcell phone applications). That is, the size of the through hole 317,317′, 317″ can advantageously provide the desired value for the lowfrequency roll off (e.g., there is a correlation between the size of thethrough hole and the value of the low frequency roll off).

The diaphragm 319, 319′, 319″ of the microphone 300A, 300B, 300C has asingle piezoelectric layer structure that advantageously provides highersensitivity (about 2-3 dB higher) and better low-frequency roll-offcontrol (−3 dB frequency) than cantilever structures with the samepiezoelectric layer. The diaphragm 319, 319′, 319″ with singlepiezoelectric layer structure also has lower sensitivity than amulti-layer diaphragm.

FIGS. 9A-9J show cross-sectional views of structures illustrating stepsof a method 400 of manufacturing a piezoelectric MEMS microphone. ThoughFIGS. 9A-9J show the method 400 for manufacturing the microphone 300A,one of skill in the art will recognize that the method 400 can also beused to manufacture the microphone 300B.

FIG. 9A shows the step of forming or providing 402 a piezoelectricsubstrate 310 and an adhesive layer 313, 313′ over the piezoelectricsubstrate 310, 310′. Optionally, the piezoelectric substrate 310, 310′can be made of Lithium Niobate (LiNbO3) or Lithium Tantalate (LiTaO3).

FIG. 9B shows the step of forming or providing 404 a substrate 301, 301′with an oxidation layer 311, 311′ on one or both of a top surface and abottom surface of the substrate 301, 301′. Optionally, the oxidizing canbe performed with a thermal oxidation furnace. In one implementation,the oxidation layer 311, 311′ optionally has a thickness ofapproximately 2-3 μm. The top oxidation layer can provide isolationbetween the substrate 301, 301′ and the piezoelectric substrate 310,310′, as further discussed below. The bottom oxidation layer can be usedas a hard mask to define a window for later etching the opening 320,320′ into the microphone 300A, 300B. The substrate 301, 301′ can be madeof Silicon, and the oxidation layers can be of Silicon dioxide.

FIG. 9C shows the step of bonding 406 the substrate 301, 301′ to thepiezoelectric substrate 310, 310′. The piezoelectric substrate 310, 310′can be flipped or rotated, so the adhesive layer 313 is facing down, andplaced on top of the substrate 301, 301′ so that the adhesive layer 313contacts the top oxidation layer 311, 311′.

FIG. 9D shows the step of thinning 408 the piezoelectric substrate 310,310′ to form the piezoelectric film 309, 309′ (e.g., to form the singlepiezoelectric film 309, 309′). In one implementation, the piezoelectricfilm 309, 309′ can have a thickness of approximately 500 nm. Thinningtechniques such as an ion slicing process and/or chemical mechanicalpolishing (CMP) process can optionally be used.

FIG. 9E shows the step of forming or providing 410 the electrode 315,315′ on the piezoelectric film 309, 309′ (e.g., depositing andpatterning, such as using wet etching, dry etching, etc., the electrode315, 315′ on the piezoelectric film 309, 309′). Optionally, theelectrode can be formed or applied 410 using a sputter machine andpatterned by dry etching (e.g., using Reactive Ion Etch (RIE) and/orInductively Coupled Plasma (ICP) etch). In one implementation, theelectrode optionally has a thickness of approximately 30 nm.

FIG. 9E also shows the step of forming or providing (e.g., depositing)412 the passivation layer 318, 318′ on top of the electrode 315, 315′and/or the piezoelectric film 309, 309′. Optionally, the passivationlayer can be formed or applied 412 using a sputter machine or a ChemicalVapor Deposition (CVD) machine. In one implementation, the passivationlayer optionally has a thickness of approximately 50 nm. The passivationlayer 318, 318′ can serve to protect the top of the microphone 300A,300B.

FIG. 9F shows the step of forming (e.g., etching) 414 vias in thestructure. Optionally, the vias can be etched using an InductivelyCoupled Plasma (ICP) etch machine and process. FIG. 9F also shows thestep of forming or providing (e.g., patterning) 416 bond pads 316, 316′.Optionally, the one or more bond pads can be formed or applied 416 usinga sputter machine, or an E-beam evaporator and lift-off process.

FIG. 9G shows the step of forming (e.g., etching) 418 the through hole317, 317′ in the structure (e.g., through the passivation layer 318,318′, piezoelectric film 309, 309′, and top oxidation layer 311, 311′).

FIG. 9H shows the step of forming 420 a top protection layer (e.g., asilicon dioxide layer) on top of (e.g., adjacent to, attached to) thepassivation layer 318, 318′ and the bond pads 316, 316′. Optionally, thetop protection layer can be formed or applied 420 using a PlasmaEnhanced Chemical Vapor Deposition (PECVD) machine and process. In oneimplementation, the top protection layer optionally has a thickness ofapproximately 2 μm.

FIG. 9H also shows the step of forming (e.g., etching) 422 the bottomoxide layer of the substrate 301, 301′ to provide a hard mask.Optionally, the patterning and etching 422 of the oxide layer on thebottom of the substrate can be performed using a Reactive Ion Etch (RIE)and/or Inductively Coupled Plasma (ICP) etch machine and process.

FIG. 9I shows the step of forming (e.g., etching) 424 the opening 320,320′ in the substrate 301, 301′ underneath the diaphragm 319, 319′.Optionally, the etching 424 of the substrate can be performed using aDeep Reactive Ion Etching (DRIE) machine and process.

FIG. 9J shows the step of removing (e.g., etching) 426 the topprotection layer (e.g., oxide layer) from on top of the passivationlayer 318, 318′ and bond pads 316, 316′ and from a bottom of thesubstrate 301, 301′ to provide the finished microphone 300A, 300B.Optionally, the removing (e.g., etching) 426 of the protection layer,oxide layer on the bottom of the substrate and oxide layer under thepiezoelectric film can be performed using a Vapor Hydrogen Fluoride(VHF) etch machine and process. The opening 320, 320′ allows soundpressure to pass therethrough to exert a force on the diaphragm 319,319′ to deflect the diaphragm 319, 319′.

FIGS. 10A-10J show cross-sectional views of structures illustratingsteps of a method 500 of manufacturing a piezoelectric MEMS microphone.In one implementation, the method 500 can be used to manufacture apiezoelectric MEMS microphone similar to the microphone 300C having acircular shape.

FIG. 10A shows the step of forming or providing 502 a piezoelectricsubstrate (e.g., similar to the piezoelectric substrate 310″), formingor providing 504 a first electrode (e.g., similar to the first electrode314″), such as by depositing the first electrode on top of thepiezoelectric substrate, and forming or providing 506 an adhesive layer313″ over the first electrode and/or the piezoelectric substrate.Optionally, the piezoelectric substrate can be made of Lithium Niobate(LiNbO3) or Lithium Tantalate (LiTaO3). Optionally, the first electrodecan be formed or applied 504 using a sputter machine and patterned bydry etching (e.g., using Reactive Ion Etch (RIE) and/or InductivelyCoupled Plasma (ICP) etch). In one implementation, the first electrodeoptionally has a thickness of approximately 30 nm.

FIG. 10B shows the step of forming or providing 508 a substrate (e.g.,similar to the substrate 301″) with an oxidation layer (e.g., similar tothe oxidation layer 311″) on one or both of a top surface and a bottomsurface of the substrate. Optionally, the oxidizing can be performedwith a thermal oxidation furnace. In one implementation, the oxidationlayer optionally has a thickness of approximately 2-3 μm. The topoxidation layer can provide isolation between the substrate and thepiezoelectric substrate, as further discussed below. The bottomoxidation layer can be used as a hard mask to define a window for lateretching an opening (e.g., similar to the opening 320″) into thepiezoelectric MEMS microphone. The substrate can be made of Silicon, andthe oxidation layers can be of Silicon dioxide.

FIG. 10C shows the step of bonding 510 the substrate to thepiezoelectric substrate. The piezoelectric substrate can be flipped orrotated, so the adhesive layer 313″ is facing down, and placed on top ofthe substrate so that the adhesive layer 313″ contacts the top oxidationlayer.

FIG. 10D shows the step of thinning 512 the piezoelectric substrate toform the piezoelectric film (e.g., similar to the piezoelectric film309″), for example to form the single piezoelectric film. In oneimplementation, the piezoelectric film can have a thickness ofapproximately 500 nm. Thinning techniques such as an ion slicing processand/or chemical mechanical polishing (CMP) process can optionally beused.

FIG. 10E shows the step of forming or providing 514 a second electrode(e.g., similar to the second electrode 315″) on the piezoelectric film(e.g., depositing and patterning, such as using wet etching, dryetching, etc., the second electrode on the piezoelectric film).Optionally, the electrode can be formed or applied 514 using a sputtermachine and patterned by dry etching (e.g., using Reactive Ion Etch(RIE) and/or Inductively Coupled Plasma (ICP) etch). In oneimplementation, the electrode optionally has a thickness ofapproximately 30 nm.

FIG. 10E also shows the step of forming or providing (e.g., depositing)515 an elastic layer (e.g., similar to the elastic layer 312″) on top ofthe second electrode and/or the piezoelectric film. In oneimplementation, the elastic layer optionally has a thickness ofapproximately 500 nm.

FIG. 10F shows the step of forming (e.g., etching) 516 vias in thestructure. Optionally, the vias can be etched using an InductivelyCoupled Plasma (ICP) etch machine and process. FIG. 1OF also shows thestep of forming or providing (e.g., patterning) 518 bond pads (e.g.,similar to bond pads 316″). Optionally, the one or more bond pads can beformed or applied 518 using a sputter machine, or an E-beam evaporatorand lift-off process.

FIG. 10G shows the step of forming (e.g., etching) 520 a through hole(e.g., similar to the through hole 317″) in the structure (e.g., throughthe elastic layer, piezoelectric film, adhesive layer 313″, and topoxidation layer).

FIG. 10H shows the step of forming 522 a top protection layer (e.g., asilicon dioxide layer) on top of (e.g., adjacent to, attached to) theelastic layer and the bond pads. Optionally, the top protection layercan be formed or applied 522 using a Plasma Enhanced Chemical VaporDeposition (PECVD) machine and process. In one implementation, the topprotection layer optionally has a thickness of approximately 2 μm.

FIG. 10H also shows the step of forming (e.g., etching) 524 the bottomoxide layer of the substrate to provide a hard mask. Optionally, thepatterning and etching 524 of the oxide layer on the bottom of thesubstrate can be performed using a Reactive Ion Etch (RIE) and/orInductively Coupled Plasma (ICP) etch machine and process.

FIG. 10I shows the step of forming (e.g., etching) 526 an opening (e.g.,similar to the opening 320″) in the substrate underneath the diaphragmdefined by the piezoelectric film and the elastic layer. Optionally, theetching 526 of the substrate can be performed using a Deep Reactive IonEtching (DRIE) machine and process.

FIG. 10J shows the step of removing (e.g., etching) 528 the topprotection layer (e.g., oxide layer) from on top of the elastic layerand bond pads and from a bottom of the substrate to provide the finishedpiezoelectric MEMS microphone. Optionally, the removing (e.g., etching)528 of the protection layer, oxide layer on the bottom of the substrateand oxide layer under the piezoelectric film can be performed using aVapor Hydrogen Fluoride (VHF) etch machine and process. The opening(e.g., similar to the opening 320″) allows sound pressure to passtherethrough to exert a force on the diaphragm to deflect the diaphragm.

FIGS. 11A-11J show cross-sectional views of structures illustratingsteps of a method 600 of manufacturing a piezoelectric MEMS microphone.In one implementation, the method 600 can be used to manufacture apiezoelectric MEMS microphone similar to the microphone 300C having acircular shape.

FIG. 11A shows the step of forming or providing 602 a piezoelectricsubstrate (e.g., similar to the piezoelectric substrate 310″), formingor providing 604 a first electrode (e.g., similar to the first electrode314″), such as by depositing the first electrode on top of thepiezoelectric substrate, and forming or providing 606 an adhesive layer313″ over the first electrode and/or the piezoelectric substrate.Optionally, the piezoelectric substrate can be made of Lithium Niobate(LiNbO3) or Lithium Tantalate (LiTaO3). Optionally, the first electrodecan be formed or applied 604 using a sputter machine and patterned bydry etching (e.g., using Reactive Ion Etch (RIE) and/or InductivelyCoupled Plasma (ICP) etch). In one implementation, the first electrodeoptionally has a thickness of approximately 30 nm.

FIG. 11B shows the step of forming or providing 608 a substrate (e.g.,similar to the substrate 301″) with an oxidation layer (e.g., similar tothe oxidation layer 311″) on one or both of a top surface and a bottomsurface of the substrate. Optionally, the oxidizing can be performedwith a thermal oxidation furnace. In one implementation, the oxidationlayer optionally has a thickness of approximately 2-3 μm. The topoxidation layer can provide isolation between the substrate and thepiezoelectric substrate, as further discussed below. The bottomoxidation layer can be used as a hard mask to define a window for lateretching an opening (e.g., similar to the opening 320″) into thepiezoelectric MEMS microphone. The substrate can be made of Silicon, andthe oxidation layers can be of Silicon dioxide.

FIG. 11C shows the step of forming (e.g., etching) 610 the top oxidelayer of the substrate to provide a hard mask. Optionally, thepatterning and etching 524 of the oxide layer on the top of thesubstrate can be performed using a Reactive Ion Etch (RIE) and/orInductively Coupled Plasma (ICP) etch machine and process.

FIG. 11D shows the step of forming (e.g., etching) 612 an opening (e.g.,similar to the opening 320″) in the substrate and oxidation layers todefine spaced apart substrate portions. Optionally, the etching 612 ofthe substrate can be performed using a Deep Reactive Ion Etching (DRIE)machine and process.

FIG. 11E shows the step of bonding 614 the substrate portions to thepiezoelectric substrate. The piezoelectric substrate can be flipped orrotated, so the adhesive layer 313″ is facing down, and placed on top ofthe sub strate portions so that the adhesive layer 313″ contacts the topoxidation layer of the substrate portions.

FIG. 11F shows the step of thinning 616 the piezoelectric substrate toform the piezoelectric film (e.g., similar to the piezoelectric film309″), for example to form the single piezoelectric film. In oneimplementation, the piezoelectric film can have a thickness ofapproximately 500 nm. Thinning techniques such as an ion slicing processand/or chemical mechanical polishing (CMP) process can optionally beused.

FIG. 11G shows the step of forming or providing 618 a second electrode(e.g., similar to the second electrode 315″) on the piezoelectric film(e.g., depositing and patterning, such as using wet etching, dryetching, etc., the second electrode on the piezoelectric film).Optionally, the electrode can be formed or applied 618 using a sputtermachine and patterned by dry etching (e.g., using Reactive Ion Etch(RIE) and/or Inductively Coupled Plasma (ICP) etch). In oneimplementation, the electrode optionally has a thickness ofapproximately 30 nm.

FIG. 11G also shows the step of forming or providing (e.g., depositing)620 an elastic layer (e.g., similar to the elastic layer 312″) on top ofthe second electrode and/or the piezoelectric film. In oneimplementation, the elastic layer optionally has a thickness ofapproximately 500 nm.

FIG. 11H shows the step of forming (e.g., etching) 622 vias in thestructure. Optionally, the vias can be etched using an InductivelyCoupled Plasma (ICP) etch machine and process.

FIG. 11H also shows the step of forming or providing (e.g., patterning)624 bond pads (e.g., similar to bond pads 316″). Optionally, the one ormore bond pads can be formed or applied 518 using a sputter machine, oran E-beam evaporator and lift-off process.

FIG. 11I shows the step of forming (e.g., etching) 626 a through hole(e.g., similar to the through hole 317″) in the structure (e.g., throughthe elastic layer, piezoelectric film, adhesive layer 313″, and topoxidation layer).

In use, the microphone structure 300A, 300B, 300C is mounted on aprinted circuit board (PCB) so that the opening 320, 320′, 320″ isdisposed over or otherwise generally aligned with an opening in the PCBthrough which sound pressure enters into the opening 320, 320′, 320″ todeflect the diaphragm 319, 319′, 319″ as discussed above.Advantageously, the piezoelectric substrate 310, 310′, 310″ hassubstantially zero residual stress (e.g., has zero residual stress), sothat the piezoelectric film 309, 309′, 309″ formed by thinning thepiezoelectric substrate or wafer 310′, 310′, 310″ likewise hassubstantially zero (e.g., zero) residual stress.

While certain embodiments of the inventions have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the disclosure. Indeed, the novel methodsand systems described herein may be embodied in a variety of otherforms. Furthermore, various omissions, substitutions and changes in thesystems and methods described herein may be made without departing fromthe spirit of the disclosure. The accompanying claims and theirequivalents are intended to cover such forms or modifications as wouldfall within the scope and spirit of the disclosure. Accordingly, thescope of the present inventions is defined only by reference to theappended claims.

Features, materials, characteristics, or groups described in conjunctionwith a particular aspect, embodiment, or example are to be understood tobe applicable to any other aspect, embodiment or example described inthis section or elsewhere in this specification unless incompatibletherewith. All of the features disclosed in this specification(including any accompanying claims, abstract and drawings), and/or allof the steps of any method or process so disclosed, may be combined inany combination, except combinations where at least some of suchfeatures and/or steps are mutually exclusive. The protection is notrestricted to the details of any foregoing embodiments. The protectionextends to any novel one, or any novel combination, of the featuresdisclosed in this specification (including any accompanying claims,abstract and drawings), or to any novel one, or any novel combination,of the steps of any method or process so disclosed.

Furthermore, certain features that are described in this disclosure inthe context of separate implementations can also be implemented incombination in a single implementation. Conversely, various featuresthat are described in the context of a single implementation can also beimplemented in multiple implementations separately or in any suitablesubcombination. Moreover, although features may be described above asacting in certain combinations, one or more features from a claimedcombination can, in some cases, be excised from the combination, and thecombination may be claimed as a subcombination or variation of asubcombination.

Moreover, while operations may be depicted in the drawings or describedin the specification in a particular order, such operations need not beperformed in the particular order shown or in sequential order, or thatall operations be performed, to achieve desirable results. Otheroperations that are not depicted or described can be incorporated in theexample methods and processes. For example, one or more additionaloperations can be performed before, after, simultaneously, or betweenany of the described operations. Further, the operations may berearranged or reordered in other implementations. Those skilled in theart will appreciate that in some embodiments, the actual steps taken inthe processes illustrated and/or disclosed may differ from those shownin the figures. Depending on the embodiment, certain of the stepsdescribed above may be removed, others may be added. Furthermore, thefeatures and attributes of the specific embodiments disclosed above maybe combined in different ways to form additional embodiments, all ofwhich fall within the scope of the present disclosure. Also, theseparation of various system components in the implementations describedabove should not be understood as requiring such separation in allimplementations, and it should be understood that the describedcomponents and systems can generally be integrated together in a singleproduct or packaged into multiple products.

For purposes of this disclosure, certain aspects, advantages, and novelfeatures are described herein. Not necessarily all such advantages maybe achieved in accordance with any particular embodiment. Thus, forexample, those skilled in the art will recognize that the disclosure maybe embodied or carried out in a manner that achieves one advantage or agroup of advantages as taught herein without necessarily achieving otheradvantages as may be taught or suggested herein.

Conditional language, such as “can,” “could,” “might,” or “may,” unlessspecifically stated otherwise, or otherwise understood within thecontext as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements, and/or steps. Thus, such conditional language is notgenerally intended to imply that features, elements, and/or steps are inany way required for one or more embodiments or that one or moreembodiments necessarily include logic for deciding, with or without userinput or prompting, whether these features, elements, and/or steps areincluded or are to be performed in any particular embodiment.

Conjunctive language such as the phrase “at least one of X, Y, and Z,”unless specifically stated otherwise, is otherwise understood with thecontext as used in general to convey that an item, term, etc. may beeither X, Y, or Z. Thus, such conjunctive language is not generallyintended to imply that certain embodiments require the presence of atleast one of X, at least one of Y, and at least one of Z.

Language of degree used herein, such as the terms “approximately,”“about,” “generally,” and “substantially” as used herein represent avalue, amount, or characteristic close to the stated value, amount, orcharacteristic that still performs a desired function or achieves adesired result. For example, the terms “approximately”, “about”,“generally,” and “substantially” may refer to an amount that is withinless than 10% of, within less than 5% of, within less than 1% of, withinless than 0.1% of, and within less than 0.01% of the stated amount. Asanother example, in certain embodiments, the terms “generally parallel”and “substantially parallel” refer to a value, amount, or characteristicthat departs from exactly parallel by less than or equal to 15 degrees,10 degrees, 5 degrees, 3 degrees, 1 degree, or 0.1 degree.

The scope of the present disclosure is not intended to be limited by thespecific disclosures of preferred embodiments in this section orelsewhere in this specification, and may be defined by claims aspresented in this section or elsewhere in this specification or aspresented in the future. The language of the claims is to be interpretedbroadly based on the language employed in the claims and not limited tothe examples described in the present specification or during theprosecution of the application, which examples are to be construed asnon-exclusive.

Of course, the foregoing description is that of certain features,aspects and advantages of the present invention, to which variouschanges and modifications can be made without departing from the spiritand scope of the present invention. Moreover, the shielded inductor neednot feature all of the objects, advantages, features and aspectsdiscussed above. Thus, for example, those of skill in the art willrecognize that the invention can be embodied or carried out in a mannerthat achieves or optimizes one advantage or a group of advantages astaught herein without necessarily achieving other objects or advantagesas may be taught or suggested herein. In addition, while a number ofvariations of the invention have been shown and described in detail,other modifications and methods of use, which are within the scope ofthis invention, will be readily apparent to those of skill in the artbased upon this disclosure. It is contemplated that various combinationsor subcombinations of these specific features and aspects of embodimentsmay be made and still fall within the scope of the invention.Accordingly, it should be understood that various features and aspectsof the disclosed embodiments can be combined with or substituted for oneanother in order to form varying modes of the discussed shieldedinductor.

What is claimed is:
 1. A piezoelectric microelectromechanical systemsmicrophone, comprising: a substrate defining an opening between a bottomend of the substrate and a top end of the substrate; a singlepiezoelectric film layer formed by thinning a piezoelectric waferdisposed over the top end of the substrate and defining a diaphragmstructure, the single piezoelectric film layer having substantially zeroresidual stress; and an electrode disposed over the diaphragm structure,wherein the diaphragm structure is configured to deflect when subjectedto sound pressure via the opening in the substrate.
 2. The microphone ofclaim 1 wherein the electrode disposed over the diaphragm structureincludes a circumferential electrode disposed over a circumference ofthe diaphragm structure and a center electrode disposed generally over acenter of the diaphragm structure, at least a portion of the centerelectrode spaced apart from the circumferential electrode.
 3. Themicrophone of claim 2 wherein the circumferential electrode is dividedinto two or more circumferential electrode portions by one or more gapstherebetween and the center electrode is divided into two or more centerelectrode portions by one or more gaps therebetween to provide amicrophone with a desired sensitivity and capacitance.
 4. The microphoneof claim 1 wherein the electrode disposed over the diaphragm structureinclude a peripheral electrode having side electrode portions disposedadjacent side edges of the diaphragm structure, the side electrodeportions spaced apart from each other, and a center electrode disposedgenerally over a center of the diaphragm structure, at least a portionof the center electrode spaced apart from the peripheral electrode. 5.The microphone of claim 1 further comprising a through hole in thediaphragm structure that extends from a top surface of the diaphragmstructure to a bottom surface of the diaphragm structure, the throughhole configured to define a low frequency roll off for the microphone.6. The microphone of claim 1 further comprising a second electrodeinterposed between the substrate and a bottom surface of thepiezoelectric film layer.
 7. The microphone of claim 6 furthercomprising an elastic layer disposed at least partially adjacent anupper surface or a bottom surface of the piezoelectric film layer, oneof the electrode and the second electrode being interposed between atleast a portion of the elastic layer and at least a portion of thepiezoelectric film layer.
 8. A radiofrequency module, comprising: aprinted circuit board including a substrate layer; one or morepiezoelectric microelectromechanical systems microphones mounted on theprinted circuit board, each microphone including: a substrate definingan opening between a bottom end of the substrate and a top end of thesubstrate, a single piezoelectric film layer disposed over the top endof the substrate and defining a diaphragm structure, the singlepiezoelectric film layer having substantially zero residual stress, andan electrode disposed over the diaphragm structure, the diaphragmstructure configured to deflect when subjected to sound pressure via theopening in the substrate.
 9. The radiofrequency module of claim 8wherein the electrode disposed over the diaphragm structure includes acircumferential electrode disposed over a circumference of the diaphragmstructure and a center electrode disposed generally over a center of thediaphragm structure, at least a portion of the center electrode spacedapart from the circumferential electrode.
 10. The radiofrequency moduleof claim 9 wherein the circumferential electrode is divided into two ormore circumferential electrode portions by one or more gaps therebetweenand the center electrode is divided into two or more center electrodeportions by one or more gaps therebetween to provide a microphone with adesired sensitivity and capacitance.
 11. The radiofrequency module ofclaim 8 wherein the electrode disposed over the diaphragm structureinclude a peripheral electrode having side electrode portions disposedadjacent side edges of the diaphragm structure, the side electrodeportions spaced apart from each other, and a center electrode disposedgenerally over a center of the diaphragm structure, at least a portionof the center electrode spaced apart from the peripheral electrode. 12.The radiofrequency module of claim 8 further comprising a through holein the diaphragm structure that extends from a top surface of thediaphragm structure to a bottom surface of the diaphragm structure, thethrough hole configured to define a low frequency roll off for themicrophone.
 13. The radiofrequency module of claim 8 further comprisinga second electrode interposed between the substrate and a bottom surfaceof the piezoelectric film layer.
 14. The radiofrequency module of claim13 further comprising an elastic layer disposed at least partiallyadjacent an upper surface or a bottom surface of the piezoelectric filmlayer, one of the electrode and second electrode being interposedbetween at least a portion of the elastic layer and at least a portionof the piezoelectric film layer.
 15. A wireless mobile devicecomprising: one or more antennas; a front end system that communicateswith the one or more antennas; and one or more piezoelectricmicroelectromechanical systems microphones mounted on a substrate layer,each microphone including: a substrate defining an opening between abottom end of the substrate and a top end of the substrate, a singlepiezoelectric film layer disposed over the top end of the substrate anddefining a diaphragm structure, the single piezoelectric film layerhaving substantially zero residual stress, and an electrode disposedover the diaphragm structure, the diaphragm structure configured todeflect when subjected to sound pressure via the opening in thesubstrate.
 16. The wireless mobile device of claim 15 wherein theelectrode disposed over the diaphragm structure includes acircumferential electrode disposed over a circumference of the diaphragmstructure and a center electrode disposed generally over a center of thediaphragm structure, at least a portion of the center electrode spacedapart from the circumferential electrode.
 17. The wireless mobile deviceof claim 16 wherein the circumferential electrode is divided into two ormore circumferential electrode portions by one or more gaps therebetweenand the center electrode is divided into two or more center electrodeportions by one or more gaps therebetween to provide a microphone with adesired sensitivity and capacitance.
 18. The wireless mobile device ofclaim 15 wherein the electrode disposed over the diaphragm structureinclude a peripheral electrode having side electrode portions disposedadjacent side edges of the diaphragm structure, the side electrodeportions spaced apart from each other, and a center electrode disposedgenerally over a center of the diaphragm structure, at least a portionof the center electrode spaced apart from the peripheral electrode. 19.The wireless mobile device of claim 15 further comprising a through holein the diaphragm structure that extends from a top surface of thediaphragm structure to a bottom surface of the diaphragm structure, thethrough hole configured to define a low frequency roll off for themicrophone.
 20. The wireless mobile device of claim 15 furthercomprising a second electrode interposed between the substrate and abottom surface of the piezoelectric film layer.
 21. The wireless mobiledevice of claim 20 further comprising an elastic layer disposed at leastpartially adjacent an upper surface or a bottom surface of thepiezoelectric film layer, one of the electrode and second electrodebeing interposed between at least a portion of the elastic layer and atleast a portion of the piezoelectric film layer.